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Assets Held for Sale - Additional Information (Detail) (USD $)
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9 Months Ended | 12 Months Ended | |
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Sep. 30, 2013
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Dec. 31, 2012
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Mar. 31, 2013
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| Assets Held for Sale, Liabilities related to Assets Held for Sale and Insurance Proceeds [Line Items] | |||
| Contract receivable | $ 75,130,000 | $ 60,535,000 | |
| Assets held for sale, fair value | 13,500,000 | ||
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Cheviot Project [Member]
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| Assets Held for Sale, Liabilities related to Assets Held for Sale and Insurance Proceeds [Line Items] | |||
| Contract receivables monthly payments | 200,000 | ||
| Contract receivables monthly payments end date | Feb. 28, 2013 | ||
| Contract receivable | 30,900,000 | ||
| Provision for loss on contract receivable | $ 14,500,000 |